The present invention relates to testing audio speakers and in particular to testing proper sealing of speaker enclosures.
Sound waves are generated both by the face of a speaker and by the rear surface. Generally (but not always), only the sound waves from the face of the speaker are intended to produce the sound heard by a listener. Sound waves produced by the rear of the speaker are out of phase with the sound waves produced by the face of the speaker, and these two sources of sound waves may cancel each other. As a result, if the sound waves from the rear of the speaker escape into the room, they may interfere with the sound produced by the face of the speaker. A known solution is to construct airtight speaker enclosures to reduce this interference and enhance speaker performance.
Known methods for air leak testing include:
underwater air bubble leak testing (too slow and too cumbersome of a test);
listening to possible leak locations using a tube or stethoscope attached to a trained listener's ear while playing low frequency sine waves (too slow, requires training, subjective and not accurate);
measuring how long the enclosure can hold a given pressure (hard to measure accurately with inherently leaky enclosures);
acoustically measure the turbulent air noise generated by air leaks and algorithmically determine if the recorded noise from the speaker exhibits air leaks (uncertain accuracy); and
measure the directional acoustic particle velocity of known leak-prone areas of the speaker enclosure and compare these values to a threshold (untested method without established thresholds).
Thus, these known methods are labor intensive, slow, and require a well-trained technician to correctly identify air leaks.